Novel tactile feedback system for robotic surgery

ABSTRACT

Apparatuses and methods for the haptic sensation of forces at a remote location. Groups of MEMS-based pressure sensors are combined into sensor arrays. In some embodiments, the pressure sensors are encased in silicone or other elastomeric substance to allow for routine use in the aqueous environment of the body. The sensor arrays may be housed in a bio-compatible material (e.g., stainless steel, plastic) and may be attached to a printed circuit board to allow the electrical signal generated by the sensors to be communicated to a user. The sensor arrays may be used with faceplates that directly interact with the target tissue or object. The faceplates may be rough, smooth, serrated, or any other texture. The present apparatuses and methods are particularly well suited for robotic surgery and may be used wherever haptic sensing of forces at a remote location is desired.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. patent application Ser. No. 13/605,098,filed Sep. 6, 2012, which claims the benefit of U.S. Provisional PatentApplication No. 61/531,266, filed Sep. 6, 2011, both of which are herebyincorporated by reference.

FIELD

The present disclosure relates generally to the field of surgery andspecifically to methods and systems for robotic and laparoscopic surgeryproviding improved tactile sensation to the surgeon.

BACKGROUND

Surgical robots with complex maneuvering capabilities are able toperform surgery by entering the body through tiny incisions. This lessinvasive approach results in decreased blood loss, significantly reducedrecovery time, and lower overall healthcare costs when compared withtraditional open surgery. For these reasons, robotic surgical systemsare becoming a valuable asset to most major surgical centers. However,the use of surgical robots is currently limited to a small number ofsimple procedures because of one constraint: the design of currentsurgical robotic tools fails to provide the surgeon with an adequatesense of the forces being exerted on the tissue by the surgicalinstruments. This sensory input, termed tactile perception, is vitallyimportant to medical professionals during surgical manipulation oftissue.

In traditional surgery, surgeons use the tactile perception of theirfingertips to ascertain how hard to pull and grasp tissue withoutcausing unwanted damage. Surgeons also use their tactile perception toassess the stiffness, density or texture of different tissues todetermine what type of tissue it is. In minimally invasive roboticsurgery, this tactile perception is lost and surgeons are left “blind”as to touch. This lack of haptic sensation poses the risk of unnecessarytissue damage and loss of valuable tactile information, and in manysurgeries this risk outweighs the benefits that accompany roboticsurgery. Thus; robotic surgery is excluded from use in many surgicalprocedures where it would prove extremely useful.

Ideally, a surgical tool for use in minimally invasive surgery wouldsatisfy several criteria. Such a tool may include sensors capable ofproviding accurate and physiologically relevant information to thesurgeon at appropriate spatial resolution. Sensors should be able toprovide accurate measurements within the large range of pressuresexperienced at the tip of the graspers which range from very low levelsup to pressures of 900 kPa. Further, the tool would possess atissue-tool interface that allows appropriate grasping and manipulationof tissues and a profile that does not damage surrounding, non-targettissue.

Many research groups have attempted the design of surgical instrumentsthat provide improved force and tactile perception to the surgeon;however, these efforts have not generated an appropriate tool forsurgical use. One group attached strain gauges on the grasper jaws thatbend with the grasper jaws and output a voltage signal corresponding tothe amount of force exerted. Dargahi J., Najarian S. “An endoscopicforce position grasper and minimum sensors,” Canadian Journal ofElectrical and Computer Engineering, (2004) 28: 151-166. The designdisclosed therein is able to determine the magnitude and location of aforce within the jaws but does not provide force distribution maps thatmay be beneficial to a user.

Rosen et al. disclosed design of a remote control handle coupled to apair of graspers. Rosen, J., Hannaford, B., MacFarlane, M., and Sinanan,M., “Force controlled and teleoperated endoscopic grasper for minimallyinvasive surgery—Experimental performance evaluation.” IEEE Transactionson Biomedical Engineering, (1999) 46: 1212-1221. Using optical encodersand actuators, the apparatus relays forces exerted at the instrument'sjaws to the teleoperated unit. This design can potentially providevaluable information about local tissue compliance but utilizes only onebulk measurement that lacks adequate spatial resolution, potentiallycausing the surgeon to generalize inappropriately to a large tissueregion.

Other groups have used microelectromechanical systems (MEMS) technologyto develop sensor arrays to provide pressure distribution maps. DargahiJ., Najarian S. “Theorhetical and experimental analysis of apiezoelectric tactile sensor for use in endoscopic surgery” SensorReview, (2004) 24:74-83; Heo J., Chung J., Lee J., “Tactile sensorarrays using fiber Bragg grating sensors” Sensors and Actuators A:Physical, (2006) 126:312-327; Peng P., Sezen A., Rajamani R., Erdman A.“Novel MEMS stiffness sensor for force and elasticity measurements”Sensors and Actuators A, (2010) 158:10-17. However, these designs havelimited utility due to a lack of functional integration into endoscopictools (i.e., they are unable to adequately manipulate tissue),inadequate resolution due to the size of the force transducers, and/orpossess low upper limits of pressure ranges that are inappropriate forsurgical application.

King et al. reported on an innovative design to be used with the DaVinci robot which provides a low-resolution force distribution via anarray of piezoresistive force sensors. King C., Culjat M., Franco M.,Bisley, J., Cannan G., Dutson E., Gnmdfest V., “A multielement tactilefeedback system for robot-assisted minimally invasive surgery” IEEETransactions on Haptics, (2009) 2:52-56. Information from these sensorsis then transmitted to 2×3 tactile display placed on the Da Vincicontrol unit at the surgeon's fingertips. The limitations of this designare spatial resolution and certain inaccuracies associated with the useof piezoresistive force sensors. Their system also lacked a functionalgrasping surface.

Thus, there remains a longstanding, unresolved need in the medicalcommunity for surgical tools used in minimally invasive surgery thathave an effective dynamic range of force measurement and sufficientspatial resolution to selectively and effectively manipulate the targettissue, while at the same time minimizing damage to surroundingnon-target tissue. Further, the profile of such surgical tools should besuch that it has minimal impact on the tissue through which it passes enroute to the target tissue. The present disclosure addresses theseneeds.

SUMMARY

The present disclosure provides a novel system capable of providing auser with accurate information about the magnitude and spatialdistribution of forces at the interface between a surgical tool and atarget tissue. The present disclosure further allows those forces to besensed by the user through an interface that allows the surgical tool tobe used during minimally invasive surgery. The present disclosure mayinclude two main components: (1) A set of surgical instruments havingpressure sensors at strategic locations within the tool, and (2) a userinterface and control system that employs electromechanical actuation to“push back” at the user's fingertips to allow remote sensation ofpressure being applied to the tissue by the surgical tool Additionally,the profile of the presently claimed surgical devices provides forminimal damage to the tissue through which the surgical tools must passen route to the target tissue.

The apparatuses, systems, and methods of the present disclosure mayemploy sensor arrays for sensing forces at a surface, comprising aplurality of pressure sensors, wherein said plurality of pressuresensors are arranged in an array, wherein said pressure sensors aresurrounded by an elastomeric substance; a printed circuit board, whereinsaid pressure sensors are operably connected to said printed circuitboard; and a housing, wherein said housing includes said plurality ofpressure sensors, said elastomeric substance, and said printed circuitboard. The pressure sensors may be microelectromechanical system-basedpressure sensors. The elastomeric substance is preferablycorrosive-resistant and may be silicone, non-reactive gel, ornon-reactive fluid. The sensors may be placed in a housing that isfabricated from a non-corrosive substance such as metal or plastic. Insome embodiments, the pressure sensors possess a linear response toforce. When using a surgical tool, the sensor arrays of the presentdisclosure may include a faceplate that may be smooth, textured orserrated, depending on the application in which the present disclosureis employed.

BRIEF DESCRIPTION OF THE DRAWINGS

For the present disclosure to be dearly understood and readilypracticed, the present disclosure will be described in conjunction withthe following figures, wherein like reference characters designate thesame or similar elements, which figures are incorporated into andconstitute a part of the specification, wherein:

FIGS. 1A-1B provides a profile and cross-sectional view of a sensorarray of the present disclosure;

FIG. 2 displays the response profile of the sensors of the presentdisclosure;

FIG. 3 shows the spatial sensitivity of the sensor arrays of the presentdisclosure;

FIGS. 4A-4C demonstrates the limited crosstalk of the sensor arrays ofthe present disclosure;

FIG. 5A-5B provides a profile and cross-sectional view of a grasperembodiment of the present disclosure;

FIG. 6 shows a cross-sectional view of a grasper embodiment of thepresent disclosure with a face plate;

FIG. 7 displays an interface through which a user may utilize thegrasper embodiments of the present disclosure;

FIG. 8 depicts a cross-section view of an interface through which a usermay utilize the grasper embodiments of the present disclosure; and

FIG. 9 depicts two physiologic scenarios in which a grasper embodimentof the present disclosure may be used.

DETAILED DESCRIPTION

It is to be understood that the figures and descriptions of the presentdisclosure have been simplified to illustrate elements that are relevantfor a clear understanding of the disclosure, while eliminating forpurposes of clarity, other elements that may be well known.

The systems and methods of the present disclosure provide surgeons withan accurate and sensitive perception of the tissue that is beingmanipulated during robotic or laparoscopic surgery. The presentdisclosure employs sensors that allow for an improved spatial resolutionand responsiveness over a broad range of relevant pressures whencompared to prior art surgical tools.

The surgical instrument embodiments of the present disclosure preferablyinclude a plurality of micro-pressure sensors located within the base ofjaws used to manipulate tissue. In some embodiments, the micro-pressuresensors are MEMS-based sensors. When chosen appropriately, the MEMSsensor arrays are capable of providing a linear response to forcestimuli over the relevant physiological range. A representativemicro-pressure sensor is the cubic micro-pressure sensor pat numberSM5108 obtainable from Silicon Microstructures. In some embodiments, theindividual MEMS sensors are cubic and may be seemed to the circuitboard. The micro-pressure sensors may also implemented by imprinting ona thin circuit board. The sensors may be coated with a protectivesilicone elastomer layer to allow the surgical tool to operate in thewater-based environment of the body. For embodiments where the sensorarrays of the present disclosure are used in other types of corrosiveenvironments, the protective elastomeric layer may be formed from asubstance from that is resistant to whatever corrosive substances are inthe environment.

In some embodiments, the sensor element size resolution is approximately1.6 mm×1.7 mm, though this resolution may be altered by changing thesize of the sensors with resolutions of approximately 0.65 mm×0.65 mmachievable. While the present disclosure is described in the context ofa grasping embodiment, the disclosure is not so limited. The sensorarrays of the present disclosure may be used in graspers, forceps,scissors, trocars, and instrument shafts (to monitor lateraldisplacement of instruments against patient anatomy) within the contextof the present disclosure. The limited circuitry used in implementingthe sensing systems of the present disclosure allows the housing of thesurgical tool in which they are placed to be relatively small comparedto prior art surgical tools. The physical profile of the devicesemploying the sensing arrays of the present disclosure are thus reducedin size compared to prior art apparatuses and provide a concomitantreduction in ancillary tissue damage during surgery.

One embodiment of the sensing arrays of the present disclosure is shownin FIG. 1A. The sensing array displayed has a 2×4 sensor array 100. Thenumber and geometry of sensors may be varied to provide for appropriatesensory assessment of the surgical site. Broad ranges of both number andgeometry of sensors are contemplated within the scope of the presentdisclosure.

A cross-section of sensor array 100 is shown in FIG. 1B. In thisembodiment, the micro-pressure sensor is a MEMS sensor die 112. Thesensor die 112 is attached to a printed circuit board 116 at the base ofthe sensor array 100. To preserve the integrity of the sensor diceduring surgery, they are coated in silicone 108, though othernon-reactive elastomers, gels, or fluids may be used to surround thesensor 112. The silicone 108 in this embodiment is in turn surrounded bya plastic housing 104 in the shape of a grid as shown in FIG. 1A. Theplastic housing provides structure to the sensing array and allows it tobe manipulated routinely by medical professionals.

A sensing array that is appropriate for surgical use should have both alinear response to force and the ability to acutely discern and isolateforce input to the array. To assess the response profile of typicalsensing arrays of the present disclosure, a set of experiments were runin which a load was applied to the top of each element within the array.Specifically, a mounted linear bearing was used to deliver a range offorces to an individual pad of the sensor array of FIG. 1 such thateight elements were tested. Each sensor element was characterized bymeasuring voltage output from each sensor die as the load was applied tothe top of the element. As shown in FIG. 2, each sensor was found tohave a linear response up to 400 grams. The use of deformable siliconeraises the question of hysteresis, but the present sensory array designdisplays minimal hysteresis effects while providing a reproducibleresponse to the load (error bars are standard deviation, N=5).

The data are summarized in the table below.

Hysteresis (%) Sensitivity Linear Average Std. Dev. (Mv/V/g) RegressionElement 1 1.25% 0.71% 0.0346 0.988 Element 2 1.44% 0.84% 0.0352 0.990Element 3 1.62% 0.43% 0.0359 0.988 Element 4 0.00% 0.46% 0.0314 0.983Element 5 1.04% 1.07% 0.0443 0.966 Element 6 −0.32% 1.14% 0.0807 0.991Element 7 1.49% 1.37% 0.0421 0.990 Element 8 4.31% 1.87% 0.200 0.990

To assess whether the present sensor array was capable of discerningforce stimulation of a single element, a separate test was performed.Force was applied to a single element of the sensor array and the forcemeasured by all sensors was assessed. FIG. 3 shows the results of twosuch experiments in which two different elements were sequentiallytested. As is clear from the figure, the sensor arrays of the presentdisclosure display minimal cross-talk such that the force output ofindividual sensors accurately represent the forces sensed at thatspecific point on the sensor array.

Finally, the ability of the sensor arrays of the present disclosure todiscern a varied force stimulus was assessed. A synthetic tissue pad 404was constructed in which two materials were employed to stimulate a 2×4sensor array 400 of the present disclosure as shown in FIG. 4A. On thetop of the pad, a firm material 408 was placed to allow force to bedistributed to the materials below. The lower portion of the padincluded two distinct synthetic materials that differed in compliance,i.e., firmness or deformability. As shown in FIG. 4A, the portion on theleft 412 is a less compliant silicone material and the portion on theright 416 is more compliant synthetic fat material. The three mm-thicktissue pad 404 was placed on top of the sensor array 400 so that theborder between the two materials laid along the D-D plane, as shown inFIG. 4B. The pad 404 was depressed 0.5 mm and the output of the sensorarrays was measured. The sensor array detected increased forces at thesensor elements compressing the stiffer silicone element 404 compared tothe elements compressing the more compliant synthetic fat pad 416 asshown in FIG. 4C.

As a result of these experiments, it has been demonstrated that thesensor arrays of the present disclosure possess a linear response toapplied forces and additionally display a high level of spatial acuity.Thus, the sensor arrays of the present disclosure possess the desiredproperties for an effective surgical tool.

FIG. 5 shows one grasper embodiment 500 of the present disclosure thatutilizes sensor arrays as described above. As shown in profile in FIG.5A, this embodiment is a surgical tool that includes a base 504 in whichthe sensor array 508 and the accompanying electronic components arefound. The top portion includes a grasping jaw 512 that is adapted toopen and close onto the sensory array 508 to grasp an object or tissue.This embodiment also includes an arm 516 that is capable of opening andclosing the grasping jaw 512 when manipulated by a user during surgery.A face view of the base 508 and sensor array 504 is shown in FIG. 5B.The sensor array 504 is shown as a series of pads in this embodiment.The tool may be fabricated from a wide variety of bio-compatiblematerials such as stainless steel, plastic, or various composites.

In other embodiments such as shown in cross-section in FIG. 6, afaceplate 604 may be included in the surgical device and placed on topof the elastomer layer 608 and sensor die 612. As shown in FIG. 6, thesensor die is attached to a printed circuit board 616 and the overallsensor array is housed in a stainless steel or plastic frame 620. Thefaceplate 604 shown in this embodiment is serrated such as may beemployed in grasping and resecting a piece of tissue. The faceplate may,however, possess an appropriate surface for the specific task to beperformed by the medical professional utilizing the device. For example,a serrated surface may be preferred for surgical interventions such asgrasping or retraction of tissue. Similarly, the faceplate may bemodified to be a sharp surface (for scissors or trocar), a flat surface(for simple probing or palpation), or a round surface (such as aroundthe cylindrical shaft of a laparoscopic instrument) for differentsurgical processes. The micro-pressure sensors included in the presentembodiments provide for accurate, repeatable pressure distribution dataacross the face of the tool, and the faceplate allows for selective anddelicate manipulation of tissue.

In some embodiments, measurements obtained through the micro-sensors aresent to an interface to be employed by the user. In one embodiment, thesignals can he sent to a graphical display that will inform the user ofthe pressure being applied to each sensor element. The graphical displaymay represent the surface of the sensor array and provide informationabout the forces being sensed at the surface of the surgical tool. Thepresent disclosure may also be implemented, either independently or incombination with a graphical display, as a finger/joystick interface.

During use, the surgeon may manipulate the grasper joystick by pressinghis or her finger 704 against a pad 708, as shown in FIG. 7. The pad 708may rotate on a pivot 712 and the angle of displacement corresponds tothe angle of displacement of the jaws of the tool. When the surgicaltool face begins to experience the normal forces of tissue pressing atthe jaws, the pivot 712 can lock into place. The pad 708 may also employspatially mapped pins 804 driven by electrical induction to push on theuser's finger proportionally to the pressure distribution measured atthe device's jaw, thus providing the user with an accurate hapticrepresentation of the forces measured at the tool face, as shown in FIG.8. Once the pivot 712 is locked, the solenoid pins 804 may be actuatedto press at the user's fingertips with forces proportional to thepressure distribution at the tool jaw (FIG. 4). In some embodiments, theforces at pressure sensors implanted at the tip of the solenoid pins 804manipulated by the user will correlate with the forces sensed theelastomer at the tool face. The arrangement of solenoid “spring”mechanisms will mimic the compliance properties of the tissue to givethe surgeon the feel of the tissue he is grasping.

For example, if the tool were being used during an operation to removeneoplastic tissue (FIG. 9), the surgeon would be able to identify theneoplastic tissue 904 as being harder than the surrounding healthytissue 908 by employing the present disclosure. Alternatively, theinterface of the present disclosure may pulse to indicate an underlyingartery 912 as also shown in FIG. 9. Furthermore, the present disclosuremay also be used to detect structures within fascia or tissue such asunderlying non-compliant nerves. In some embodiments, sensor arrays ofthe present disclosure could be placed onto a probe which could be usedto assess firmness of tissue.

Through use of the present disclosure, surgeons and other users will beprovided with an accurate haptic sensation of important surgical cuessuch as the pulsation of an artery; the stiffness of different tissues,and the force with which they are grasping or pulling tissue.

While described in the context of surgical procedures, the present indisclosure may also be employed in a variety of circumstances whereremote haptic sensing of forces is desirable. Examples of such scenariosinclude virtual reality or simulation situations as well. Additionally,the sensor arrays of the present disclosure may also be useful in harshenvironment where exposure to humans is detrimental (e.g., corrosiveenvironments) or at locations that are difficult for humans to access.

Nothing in the above description and attached figures is meant to limitthe present disclosure to any specific materials, geometry, ororientation of elements. Many modifications are contemplated within thescope of the present disclosure and will be apparent to those skilled inthe art. The embodiments disclosed herein were presented by way ofexample only and should not be used to limit the scope of thedisclosure.

We claim:
 1. A surgical system for use in robotic surgery on a tissue,comprising; a plurality of pressure sensors, wherein the plurality ofpressure sensors includes more than four pressure sensors arranged in anarray, wherein the plurality of pressure sensors are surrounded by anelastomeric substance; a printed circuit board, wherein the plurality ofpressure sensors are operably connected to the printed circuit board;and a probe device including a faceplate, wherein the probe deviceincludes the plurality of pressure sensors, the elastomeric substance,and the printed circuit board, further wherein the faceplate is disposedadjacent to the elastomeric substance and includes a level surface forprobing or palpitation of the tissue; wherein the plurality of pressuresensors is adapted to sense forces exerted by the probe device on thetissue.
 2. The surgical system of claim 1, wherein the plurality ofpressure sensors are microelectromechanical system-based pressuresensors.
 3. The surgical system of claim 1, wherein the elastomericsubstance is selected from the group consisting of silicone,non-reactive gel, and non-reactive fluid.
 4. The surgical system ofclaim 1, wherein the probe device includes a bio-compatible metal orplastic.
 5. The surgical system of claim 1, wherein each of theplurality of pressure sensors possess a linear response to force.
 6. Thesurgical system of claim 1, wherein the sensor array includes eightpressure sensors.
 7. The surgical system of claim 6, wherein the eightpressure sensors are arranged in a 2×4 array.
 8. The surgical system ofclaim 1, further comprising a manipulation interface, wherein themanipulation interface is operably connected to the probe device and isadapted to represent a force exerted by the probe device on the tissuesuch that a user employing the manipulation interface is able to sensethe force exerted by the probe device on the tissue.
 9. The surgicalsystem of claim 8, wherein the manipulation interface includes auser-engagement member that is manually moveable by a user, whereinmovement of the user-engagement member causes corresponding displacementof the faceplate, and further wherein the user-engagement member isconfigured to lock in place when the plurality of pressure sensors sensea force of the tissue pressing against the faceplate.
 10. A surgicalsystem for use in robotic surgery on a tissue, comprising: a pluralityof pressure sensors surrounded by an elastomeric substance, wherein theplurality of pressure sensors include more than four pressure sensorsarranged in an array; a printed circuit board, wherein the plurality ofpressure sensors are operably connected to the printed circuit board; aprobe device including a surface adapted to interface with the tissue,wherein the probe device includes the plurality of pressure sensors, theelastomeric substance, and the printed circuit board, further whereinthe surface adapted to interface with the tissue is disposed adjacent tothe elastomeric substance and includes a level surface for probing orpalpitation of the tissue; and a manipulation interface, wherein themanipulation interface is operably connected to the probe device and isadapted to represent a force exerted by the probe device on the tissuesuch that a user employing the manipulation interface is able totactilely sense the force exerted by the probe device on the tissue. 11.The surgical system of claim 10, wherein the manipulation interface isconfigured to pulse to indicate to the user an underlying artery in thetissue.
 12. The surgical system of claim 10, wherein the elastomericsubstance is selected from the group consisting of silicone,non-reactive gel, and non-reactive fluid.
 13. The surgical system ofclaim 10, wherein the probe device is fabricated of a biocompatiblemetal or plastic.
 14. The surgical system of claim 10, wherein themanipulation interface includes a user-engagement member that ismanually moveable by a user, wherein movement of the user-engagementmember causes corresponding displacement of the level surface, andfurther wherein the user-engagement member is configured to lock inplace when the plurality of pressure sensors sense a force of the tissuepressing against the level surface.
 15. The surgical system of claim 10,wherein each of the plurality of pressure sensors possess a linearresponse to force.
 16. A system for conducting robotic surgery ontissue, comprising: a probe device including a faceplate having a levelsurface for probing or palpitation of a tissue; a sensor array disposedwithin the probe device, the sensor array including a plurality ofpressure sensors, wherein the plurality of pressure sensors are arrangedin an array and are surrounded by an elastomeric substance, furtherwherein the plurality of pressure sensors is adapted to sense forcesexerted by the probe device on the tissue; and a printed circuit boarddisposed within the probe device, wherein the plurality of pressuresensors is operably connected to the printed circuit board; amanipulation interface, wherein the manipulation interface is operablyconnected to the probe device and provides tactile feedback to the userrepresenting the forces exerted by the probe device on the tissue. 14.The system of claim 16, wherein the manipulation interface includes auser-engagement member that is manually moveable by a user, whereinmovement of the user-engagement member causes corresponding displacementof the faceplate, and further wherein the user-engagement member isconfigured to lock in place when the plurality of pressure sensors sensea force of the tissue pressing against the faceplate.
 18. The system ofclaim 16, wherein the manipulation interface comprises a plurality ofmoveable pins configured to provide tactile feedback representing theforces to the user.
 19. The system of claim 18, wherein the pins areconfigured to press against a user with forces proportional to theforces sensed by the plurality of pressure sensors.
 20. The system ofclaim 16, wherein each of the plurality of pressure sensors possess alinear response to force.